Apparatus for preventing backflow of liquid



Feb. 26, 1952 M. .H. GROVE APPARATUS FOR PREVENTING BACKFLOW OF LIQUID 3 Sheets-Sheet 1 Filed NOV. 8, 1947 INVENTOR Marv/ 7 /7'. 6m ve ATTORNEYS M. H. GROVE 2,586,942 APPARATUS FOR PREVENTING BACKFLOW 0F LIQUID 3 Sheets-Sheet 2 Feb. 26, 1952 Filed Nov. 8, 1947 INVENTOR Marv/n H. Grove BY wzuaw AT ORNEYS wm m nw AN ww ww Feb. 26, 1952 M. H. GROVE 2,586,942

APPARATUS FOR PREVENTING BACKFLOW OF LIQUID Filed Nov. a. 1947 s Sheets-Sheet :5

INVENTOR Mary/n H. 6m ve ATTORN EYS Patented Feb. 26, 1952 APPARATUS FOR, PREVENTING BACKFLOW OF LIQUID Marvin H. Grove, Piedmont, Calif., assignor, by

mesne assignments, to Grove Regulator Company, a corporation of California Application November 8, 1947, Serial No. 784,837

4 Claims. 1

This invention relates generally to apparatus for the purpose of preventing back flow of water from service or consumer piping to water supply mains.

Various types of apparatus have been used in conjunction with water supply systems for the purpose of preventing objectionable water contamination due to back flow of contaminated water for consumer piping to the water supply mains. One of the simplest types of apparatus to prevent such back flow consists of a check valve which opens to permit normal flow of water, and which closes in the event the consumer pressure equals or becomes greater than the supply pressure. In conjunction with such a check valve a vacuum breaker valve may also be connected to the inlet side of the same, thus serving to prevent sucking of contaminated water through the check valve due to a temporary subatmospheric pressure in the supply main.

With all of the more common types of check valves there is always some danger of leakage sufiicient to cause serious contamination, due for example to an obstruction or mechanical failure which prevents proper closure. Therefore more elaborate apparatus which affords utmost safety makes use of two check valves connected in series between the water supply mains and the consumer piping in conjunction with an automatic unloading valve serving under certain conditions to vent the space between the check valves to the atmosphere. As usually installed and adjusted the unloading valve has fluid connections to both the space between the check valves and the water supply main, and serves to vent the space between the check valves to the atmosphere when the pressure in said space attains a value substantially equal to the inlet or water supply main pressure. With such apparatus it is assumed that no contamination of the water main can occur because i the pressure upon the outlet side of the first check valve can in no event exceed the water main pressure.

Back flow preventing apparatus of the type last described has incorporated common types of check valves, which generally utilize rigid disc or flap valve members adapted to seal upon a stationary annular seat. When such a check. valve is closed pressure variations upon the outlet sidecannot be transmitted to the inlet side because the valve member and associated parts form in effect a rigid barrier between the inlet and outlet. Therefore an abnormal back pressure in the service or consumer piping cannot be transmitted to the space between said valves, during periods when no flow is occuring through the valves. In other words operation of the unloading valve can occur only when back flow leakage takes place through the second check valve. I have found that this reliance upon leakage is a distinct disadvantage, because it necessarily requires flow of contaminated water into the space between the check valves, and in addition it makes it necessary for the unloading operation to lag behind inattainment of abnormal pressure in the service or consumer piping,

thus failing to afiord the fullest amount of protection against back flow contam1nat1on.

It is an object of the present invention to provide apparatus for preventing back flow of water from water supply mains to service piping, making use of two check valves in conjunction with an automatic unloading valve as described above, but which will have the feature of causing unloading of the space between the check valves when an abnormal pressure condition occurs, without the necessity of leakage through the second check valve.

Another object of the invention is to provide apparatus of the above character which will afford improved protection against back flow contamination, and which will be highly reliable in its unloading operation.

Additional objects of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure l is a side elevational view showing apparatus incorporating the invention.

Figure 2 is a plan View partly in section show ing the two check valves and the unloading valve.

Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 1.

Figure 4 is a cross-sectional view taken along the line ld of Figure 1.

The apparatus illustrated in the drawings consists generally of a pair of serially connected check valves H and I2, in conjunction with an automatic venting or unloading valve !3. In actual commercial installations it is desirable to provide a hand operated valve M between the check valve II and the water supply piping I 6. Likewise a hand operated valve H is connected between check valve I2 and the service or consumer piping 18. In a typical instance the pipe I8 is connected with service piping of an industrial plant, and the water carried by the same may be exposed to serious contamination. The purpose of my apparatus is to provide against back flow of such contaminated water from the pipe It to the pipe l6.

In place of utilizing check valves of conventional construction, I utilize valves'of the type making use of a rubber sleeve having one end edge of the same adapted to seal upon a circular barrier. Thus the valves illustrated make use of three body parts 2|, 22 and 23, which are coupled together by suitable means such as bolts 24 and 26. The inlet passage 21 formed by body *.the annular surface '33.

tion of substantial pressure .pered wall portion 52c.

part 2! is connected directly with the piping it through the hand valve M, and the outlet passage 28 formed by' bodypart 23 is directly connected with the piping l8 through hand valve ii. The

connecting space 29 between the two check valves is formed by body part 22 and it is normally closed, except under certain pressure conditions as will be presently explained.

Mounted within the body part .22 there is an annular core 32 which is provided with. anannular seat surface 33. The periphery of core 32 On the inlet side of sealing surface 33 is provided with spaced longitudinal ribs 34, which mount the annular support ring 3-8, and the positioning lugs 31. The lugs 3'! are received within the annular recess 38 formed in the bodypart 2!. The outlet 'end of the core 32 is engaged by the lugs 39, which are carried by the body'part 22.

Surrounding the core 32 there is a resilient "rubberisleeve ii which has'one end'of the same provided with'a flange 2, for enabling the same to be gripped between the two adjacent body parts. It is desirable that this rubber sleeve be made tapered as illustrated. Thus it is formed to provide a relatively thin wall portion 41.7. which is adapted to seal upon'the surface 33, a relatively thick wall portion Mb which extends from the flange 42, and a tapered wall portion 410 which joins the relatively thin wall portion 41a with the thick wall portion'dlb.

Normally when the resilientsleeve is not being acted upon by "substantial differential pressure, the relatively thin wall portion lia assumes a contracted position in sealing engagement with However, with applicato the inlet side of the check valve, the sleeve is expanded outwardly from the sealing surface '33,'thus permitting flow of liquid. The difierential'pressure required to open this type of check valve is dependent in part upon the resiliency of the wall portion-Ma. For the check valve l l the rubber sleeve is selected to require a substantial differential "pressure to example of the order of for the check valve l2 the open the same, as for 3 to 4 p. s. i. However,

rubber sleeve i selected whereby the difierential pressure required to open the same will be negligible, as for example of the order of-from 0.3 to 0.5 p. s. i.

The working parts of the check valve l2 are substantially the same as for the check valve H. The core 46, sealing surface: 41, ribs 48, annular ring 49 and mounting tabs 5| can be substantially the same-as the corresponding parts for check valve '1 I. The resilient rubber sleeve 52 likewise is constructed with a relatively thin wall portion 52a, 2. thick wall portion 52b and a ta- Because check valve I2 is arranged to open with negligible applied differential pressure, the wall portion 52a is relatively thin compared to wall portion Ma for the check valve H.

The unloading or venting'valve l3 can vary in specific design but should be constructed and operated in such a manner as to vent the space 29 when the pressure in this space reaches a value substantially equal to thepressure in the inlet passage 21, as for example within 0.5 p. s. i. of the inlet pressure. The particular unloading valve illustratedis provided with a fluid pressure operated diaphragm, and'the chambers on op osite sides of the diaphragm are connected respectively with the inletpassage 21, and the intervening space 29. v

To more specifically describe the unloading valve illustrated, a pair of valve members 56 and 51 are carried by the movable valve stem 58 and are adapted to close upon the seats 5 9 and 6! carried by the valve body 62. A pipe 63 connects the inlet side of this valve body to the space 29. The discharge passage 64 may connect to the atmosphere or to a convenient sewer.

The valve stem 58 is attached to a fluid pressure operated diaphragm 56 which is carried by the diaphragm mounting 67. Space 58 on one side of this diaphragm is connected by pipe 69 to the inlet passage 21. The space H upon the other side of the diaphragm is connected by pipe 12 with the space 29 intervening between the two check valves. A light compression spring 12 normally urges the valves 56 and 51 toward open position. The relationship between the fluid pressure areas on opposite sides of the diaphragm, in conjunction with the compression spring '12, is such that the valve members 56 and 5'1 remain closed when the pressure in inlet '21 is substantiallygreater than the pressure-in space 29. However, if under abnormal'conditions the pressure in space 29 should attain a value substantially equal to the pressure in inlet 2?, then diaphragm 66 causes movement of the same to unseat the valve members 55 and 57, thus permit venting or unloading of liquid in space 29.

In addition to the parts described above it is desirable to provide a so-called vacuum breaker valve in communication with the space '21. As illustrated in Figure 4, such a valve 'Hican be a check valve constructed substantially the same as the check valves previously described. Thus the valve 76 includes a body 1! which 'is connected to the body part 21, an inner core'lil, and a resilient sleeve 19 which normally seals upon the core 18. Subatmospheric pressure in space 29 causes the check valve 16 to open to the atmosphere.

Each of the check valves 1 l and i2 has a peculiar characteristic not possessedby conventional types of check valves, such as are provided with a flap or like valve member closing upon a stationary annular seat. Considering the check valve H, a substantial area of the rubber sleeve 4| forms in effect a flexible diaphragm which-is interposed between the inlet and outlet passages. Assuming that some back pressure is applied after closure, the rubber tube is contracted inwardly to a smaller diameter, thus in effect increasing the outlet volume and decreasing the volume on the inlet side. The same is likewise true of the check valve l2. As will be presently explained this characteristic plays an important part in the mode of operation.

To describe the mode of operation of the apparatus, it will be presumed that it is connected substantially as illustrated in Figurel with both the manual valves H1 and H open, and with pipe 18 representing consumer piping such as may be employed in an industrial plant. In a typical instance the normal water main pressure may vary from say 60 to p. s. i. Under all normal flow conditions a predetermined diiferential is maintained across the check valve H, as for example a differential of the order of 3 or 4 p. s. i. Aspreviously explained this differential is maintained because of the pressure required to expand the rubber tube 5 I Assuming a reasonable rate of consumption from the service or consumer piping I8, both of the check valves will be held open by flow of liquid, and the unloading valve 13 will remain closed by virtue of the difierential between the pressures applied to the diaphragm 66. Under abnormal conditions the pressure in the outlet passage 28 may equal or even exceed the inlet pressure applied to passage 21. As the pressure value in passage 28 approaches that in passage 21, both of the check valves H and I2 tend to close, and when the pressure in outlet 28 substantially equals the pressure in inlet 21, pressure is transmitted through the flexible sleeve 52 to the liquid in space 29, thus causing the pressure in space 29 to be substantially the same value. Application of such pressure from space 29 to the diaphragm 66 causes this diaphragm to move to open the valves 56 and 51, thus connecting space 29 to the atmosphere. If this condition should occur at a time when there is substantial pressure in the inlet 21, and if there is no back flow leakage past check valve 12, the differential pressure across check valve II will immediately be increased whereby unloading valve I3 immediately closes. back pressure is applied from outlet 28 to a value equal to or greater than the pressure applied to inlet 21 and that there is improper closing of the check valve l2, abnormal pressure in the outlet 28 causes back leakage past the check valve l2, thus serving to maintain a pressure in space 29 at a value equal to the pressure in inlet 21. Under such conditions the unloading valve l3, after initial opening of the same, remains open to continuously vent such leakage from space 29. Thus back flow leakage past the check valve l2 can in no event reach the inlet 21.

If a temporary condition should occur in which no water is being consumed from the pipe l8, and the pressure applied to inlet 21 drops from normal by a margin slightly greater than the difierential normally maintained across the check valve I l, the rubber tube 4| tends to collapse *upon its core due to back flow pressure applied to the same. As a result the volume of space 29 is increased and the pressure in this space is relieved and caused to assume a value substantially less than that in the inlet. Therefore the unloading valve I3 is not afiected, which is desirable because such a condition is not dangerous and does not threaten water contamination. Under like conditions using apparatus having check valves of conventional construction, the unloading valve would be subject to temporary false operation.

It will be evident from the foregoing that my apparatus not only provides for operation of the unloading valve during abnormal back pressure conditions when the second check valve fails to close properly, but in addition it connects the space between the check valves to the atmosphere under certain unsafe abnormal back pressure conditions, irrespective of actual leakage through the second check valve.

I claim:

1. In valve apparatus for preventing back flow of water from consumer piping to water supply piping, a first check valve having its inlet connected to the supply piping, said check valve requiring application of a substantial pressure differential to eifect opening of the same, a second check valve having its inlet connected to the outlet of the first check valve and having its outlet connected to consumer piping, said second valve including a flexible diaphragm-like valve member interposed between the inlet and outlet passages of the same when the valve is closed and capable of substantial deflection after the valve is closed, an unloading valve movable between open and closed positions and connected to the space Assuming that between said check valves, and means serving to operate said unloading valve responsive to a condition in which the pressure in said space attains a value substantially equal to the supply pressure, said flexible valve member of the second valve being capable of deflection to transmit back pressure in the consumer piping to the space be tween the check valves to thereby cause operation of the unloading valve.

2. In valve apparatus for preventing back flow of water from consumer piping to water supply piping, a first check valve having its inlet connected to the supply piping, said valve requiring a substantial predetermined differential pressure to open the same, a second check valve having its inlet connected to the outlet of the first check valve and its outlet connected to the consumer piping, said second valve including a flexible diaphragm-like member interposed between the inlet and outlet passages of the same when the valve is closed and serving when flexed to vary the volume of the space between the check valves, and valve means for effecting automatic venting of said space, said valve means having fluid connections with both said space and the water supply piping and operative to vent said space when the pressure in said space attains a value substantially equal to the pressure of the water supply, said flexible valve member of the second valve being capable of deflection to transmit back pressure in the consumer piping to the space between the check valves to thereby cause operation of the unloading valve.

3. A valve apparatus for preventing back fiow of water from consumer piping to water supply piping, a first check Valve having its inlet connected to the supply piping, said check valve requiring application of a substantial pressure dif ferential to efiect opening of the same, a second check valve having its inlet connected to the outlet of the first check valve and its outlet connected to the service piping, there being a closed space formed between said check valves, each of said check valves including a flexible diaphragmlike valve member interposed between the inlet and outlet passages of the same when the valve is closed and capable of flexing movement to vary the volumes of the spaces on opposite sides of the same, and unloading valve means connected to said closed space and having operative fluid connections to both said space and to the inlet side of the first check valve, said venting means serving to vent said space responsive to a pressure value in said space substantially equal to the pressure applied to the inlet of the first check valve, said flexible valve member of the second valve being capable of deflection to transmit back pressure in the consumer piping to the space between the check valves to thereby cause operation of the unloading valve.

4. A valve as set forth in claim 3, in which each of the check valves includes a resilient rubber tube forming said flexible diaphragm like member.

MARVIN H. GROVE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,310,586 Lohman Feb. 9, 1943 2,328,118 Ahlport Aug. 31, 1943 2,389,412 Carlton Nov. 20, 1945 

